Autonomous radiation reference transfer method and system for satellite optical remote sensor formation

Abstract

This invention provides an autonomous radiometric reference transfer method and system for satellite optical remote sensor formations. Satellite A's multispectral wide-swath optical remote sensor observes the Earth, identifies cloud-free calibration fields or uniform regions suitable for reference transfer, generates mission guidance information, and transmits it to satellite B via an inter-satellite link. Satellite B's radiometric reference optical remote sensor, based on the mission guidance information, points its observation field of view to the designated area and sends the observation data back to satellite A via the inter-satellite link. After radiometric reference transfer calculations, calibration parameters are obtained, and radiometric correction is performed on satellite A's multispectral wide-swath optical remote sensor, completing the radiometric reference transfer. This invention can autonomously discover suitable calibration regions for radiometric reference transfer in orbit, overcoming the limitation of the limited number of ground calibration fields, and autonomously completes multi-satellite collaborative observation and radiometric reference transfer.

Description

Technical Field

[0001] This invention belongs to the field of on-orbit radiometric calibration, specifically relating to an autonomous radiometric reference transfer method and system for satellite optical remote sensor formations. Background Technology

[0002] With the development of remote sensing, it has played an increasingly important role in drought surveys, crop yield estimation, environmental degradation monitoring, and natural disaster monitoring, thus demanding quantitative applications of remote sensing data. The key to the successful use of sensors for quantitative applications lies first and foremost in radiometric calibration. Without radiometric calibration, subtle changes in ground features may be masked by the decay of sensor components and thus fail to be detected. By using space radiometric measurement benchmarks to perform traceable on-orbit radiometric calibration of other remote sensing satellites, it is possible to understand the uncertainties, errors, and variations in sensor characteristics, and to correct them in a timely manner, thereby promoting the development of quantitative remote sensing science.

[0003] Therefore, establishing an on-orbit radiometric benchmark traceable to the International Basic Unit (SI) using a space-based radiometric benchmark source and its associated transfer system, and unifying the planning of remote sensing operations, can reduce resource waste, improve the effective application of data, and enhance my country's own calibration technology and capabilities. Establishing my country's independent space-based absolute radiometric calibration benchmark system is of great significance for my country's climate, land resources and environment monitoring, and weather forecasting.

[0004] The literature (Zhang Yanna, Guo Fuxiang, Wei Wei, Li Xin. Cross-calibration method based on multi-angle apparent reflectance model [J]. Acta Photonica Sinica, 2023, 52(7): 071-2004) proposes to use a high-precision long-time series satellite multi-angle, hyperspectral apparent reflectance model. After region matching, time matching, and cloud removal, the model is used to carry out cross-calibration applications between different satellites on the ground. Compared with the radiation reference transfer method of this invention, it does not mention the innovative points of this invention, such as autonomously searching for suitable calibration areas in orbit and autonomously completing the radiation reference transfer between different payloads between satellites.

[0005] The literature (Ma Lingling, Wang Ning, Gao Caixia, et al. On-orbit absolute radiometric calibration of optical remote sensing satellites: progress and trends [J]. Journal of Remote Sensing, 2023, 27(5): 1061-1087) proposes to carry a space radiometric reference payload on a satellite and transfer a high-precision space radiometric measurement reference from the space-based standard radiometric calibration system to the operational optical remote sensing satellite by observing the target scene simultaneously with other satellite payloads. Compared with the radiometric reference transfer method of this invention, it does not mention the innovative points of this invention, such as autonomously searching for suitable calibration areas in orbit and autonomously completing the radiometric reference transfer between different payloads.

[0006] The literature (Liu Qiang, Zhu Rongchen, Zhang Donghui, et al. Design and Experiment of High-Altitude Scientific Balloon for Near-Space Radiation Reference Transfer Calibration [J]. Proceedings of the 8th National Conference on High-Resolution Earth Observation, 2022) proposed the design and implementation of a high-altitude scientific balloon system flight test, constructing a visible-shortwave infrared radiance meter as the near-space radiation reference transfer calibration payload, which flew at an altitude above 18 km for 11 hours and 21 minutes, achieving good observation results. Compared with the radiation reference transfer method of this invention, the radiation reference transfer method is different, and the innovative points of this invention are not mentioned.

[0007] The literature (Chen Xuan, Qi Wenwen, Tan Wei, He Hongyan. Analysis of Cross-Matching Constraint Mechanism Based on Satellite Joint Observation [J]. Journal of Changchun University of Science and Technology (Natural Science Edition), 2020) proposes to use the satellite's orbital parameters and calibration field information, combined with joint observation constraints, to calculate and predict the time and position information of two satellites on the ground, thereby completing the simulation of radiation reference transfer between different satellites. Compared with the radiation reference transfer method of this invention, it does not mention the innovative points of this invention, such as autonomously searching for suitable calibration areas in orbit and autonomously completing the radiation reference transfer between different payloads between satellites.

[0008] The literature (Lu Naimeng, Ding Lei, Zheng Xiaobing, et al. Space Radiometric Measurement Reference Technology in China [J]. Journal of Remote Sensing, 2020, 24(6):672-680) proposes to launch satellites with ultra-high radiometric measurement accuracy to calibrate other remote sensing satellites while monitoring climate change signals, thereby improving the overall calibration accuracy of global remote sensing satellites. Compared with the radiometric reference transfer method of this invention, it does not mention the innovative points of this invention, such as autonomously searching for suitable calibration areas in orbit and autonomously completing the radiometric reference transfer between different payloads.

[0009] Patent document CN110161533A provides an intelligent radiometric calibration system for unattended satellite optical payloads. This system includes: a satellite-ground synchronous forecasting system that acquires satellite orbit messages and calculates the start-up observation time of a UAV; an automatic atmospheric observation system that acquires meteorological and atmospheric data for the site observation area; an UAV equipped with observation equipment; an automatic UAV-based ground observation system that controls the UAV and its observation equipment to perform observation tasks within the site observation area based on the UAV's start-up observation time and the meteorological data; a ground control and data processing system for processing the observation data; a satellite data acquisition and processing system that acquires satellite data within the site observation area during the execution of the observation tasks; and a satellite radiometric calibration system that uses the observation data, satellite data, and atmospheric data as input to complete the radiometric calibration process.

[0010] However, patent document CN110161533A did not solve the technical problem of how satellite formations can autonomously search for suitable calibration areas and autonomously complete the transfer of radiation references between different payloads between satellites. Summary of the Invention

[0011] To address the shortcomings of existing technologies, the purpose of this invention is to provide an autonomous radiation reference transfer method and system for satellite optical remote sensor formations.

[0012] According to the present invention, an autonomous radiometric reference transfer method for a satellite optical remote sensor formation is provided. Satellite A, a multi-band wide-swath optical remote sensor, observes the Earth, identifies a calibration field without cloud cover or a uniform region suitable for reference transfer, generates mission guidance information, and transmits it to satellite B via an inter-satellite link. Satellite B, a radiometric reference optical remote sensor, points its observation field of view to the designated area according to the mission guidance information and sends the observation data back to satellite A via the inter-satellite link. After radiometric reference transfer calculation, calibration parameters are obtained, and radiometric correction is performed on the multi-band wide-swath optical remote sensor of satellite A to complete the radiometric reference transfer.

[0013] Preferably, it includes: Step 1: Satellite A plans the time window for calibration of the radiation reference transfer area; Step 2: Satellite A's multispectral wide-swath optical remote sensor performs Earth observation imaging, real-time positioning, and cloud detection; Step 3: During the time window, when the observation image of the satellite A multispectral wide-swath optical remote sensor covers the calibration area and there are no clouds, the ground is used as the calibration area; if the satellite A multispectral wide-swath optical remote sensor observes a deep, cold, and uniform cloud layer, that cloud layer is used as the calibration area. Step 4: Satellite A calculates the visible time window of the calibration area for the radiation reference optical remote sensor of Satellite B, and uses it as the planned time node; Step 5: If the calibration area is visible to the radiation reference optical remote sensor of satellite B, then satellite A generates mission guidance in real time and sends it to satellite B via inter-satellite link; Step 6: After receiving the mission guidance information, the radiation reference optical remote sensor on satellite B will point the observation field of view to the calibration area at the planned time node, and after completing the imaging, it will send the observation data to satellite A through the inter-satellite link; Step 7: The satellite A real-time processing and mission planning equipment calculates the calibration coefficients based on the observation data of the calibration area using the satellite A multispectral wide-swath optical remote sensor and the satellite B radiation reference optical remote sensor, and performs radiation calibration on the satellite A multispectral wide-swath optical remote sensor.

[0014] Preferably, the ground calibration area in step one is a uniformly radiated site, and the ground-based equipment is planned and uploaded to satellite A for real-time processing and mission planning.

[0015] Preferably, a standard calibration source is configured on the radiation reference optical remote sensor of satellite B, and the calibration coefficients are transferred to the multispectral wide-swath optical remote sensor of satellite A by observing the same calibration area from both satellite A and satellite B.

[0016] Preferably, satellite A and satellite B operate on the same orbital plane, with satellite A having a fixed orbital phase that is ahead of satellite B.

[0017] Preferably, the planned time node is the time when satellite B passes over the target, which is obtained by the real-time processing and mission planning equipment of satellite A based on the orbital parameters of satellite B.

[0018] Preferably, the calibration coefficients are obtained through a series of steps including inter-channel position matching, calculation of simulated apparent radiance based on an atmospheric transport model, calculation of spectral matching factors, and fitting of calibration equations.

[0019] According to the present invention, a satellite system includes satellite A and satellite B; Satellite A is equipped with real-time processing and mission planning equipment, which is used for autonomous planning of ground calibration area observation missions, autonomous observation of ground calibration areas according to planned time nodes, and generation of guidance information to coordinate with Satellite B to complete ground calibration area observations. Satellite B transmits the space radiation measurement benchmark to the multispectral wide-swath optical remote sensor of Satellite A by viewing the same calibration area as Satellite A.

[0020] Preferably, the satellite formation autonomously searches for calibration areas in orbit.

[0021] Preferably, when the satellite A multispectral wide-swath optical remote sensor observes a deep, cold, and uniform cloud layer, that cloud layer is used as the calibration area.

[0022] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention fills a gap in the existing technology and provides a method for on-orbit autonomous radiation reference transfer of space-based optical remote sensors.

[0023] 2. This invention can autonomously discover calibration regions suitable for radiation reference transfer in orbit, breaking the limitation of the limited number of ground calibration fields, and autonomously complete collaborative observation and radiation reference transfer among multiple satellites.

[0024] 3. This invention can use clouds as a calibration area, making it applicable to a wider range of meteorological conditions. Attached Figure Description

[0025] Other features, objects, and advantages of the present invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings: Figure 1 This is a schematic diagram of the on-orbit autonomous radiation reference transfer process. Figure 2 This is a schematic diagram of a multi-satellite system in orbit. Detailed Implementation

[0026] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make several changes and improvements without departing from the concept of the present invention. These all fall within the protection scope of the present invention.

[0027] This invention provides an autonomous radiometric reference transfer method for a satellite optical remote sensor formation. The method includes satellite A, satellite B, a multispectral wide-swath optical remote sensor, a radiometric reference optical remote sensor, real-time processing and mission planning equipment, etc. The multispectral wide-swath optical remote sensor is mounted on satellite A, the real-time processing and mission planning equipment is mounted on satellite A, and the infrared radiometric reference optical remote sensor is mounted on satellite B. Satellite A's multispectral wide-swath optical remote sensor observes the Earth, identifies a cloud-free calibration field or a uniform region suitable for reference transfer, generates mission guidance information, and transmits it to satellite B via an inter-satellite link. Satellite B's radiometric reference optical remote sensor points its observation field of view to the designated area according to the mission guidance information and sends the observation data back to satellite A via the inter-satellite link. After radiometric reference transfer calculations, calibration parameters are obtained, and radiometric correction is performed on satellite A's multispectral wide-swath optical remote sensor, completing the radiometric reference transfer.

[0028] like Figure 1 As shown, this invention provides an autonomous radiometric reference transfer method for satellite optical remote sensor formations, comprising the following steps: Step 1: Satellite A's real-time processing and mission planning equipment continuously plans the time window for the ground calibration area that can be used for radiation reference transfer; Step 2: Satellite A's multispectral wide-swath optical remote sensor performs Earth observation imaging, and Satellite A's real-time processing and mission planning equipment performs real-time positioning and cloud detection on the observation images from Satellite A's multispectral wide-swath optical remote sensor. Step 3: During the time window, when the observation image from the multispectral wide-swath optical remote sensor of satellite A covers the calibration area and there are no clouds, the ground serves as the calibration area and can be used for the transfer of radiation references between satellite A and satellite B. The system includes a multispectral wide-swath optical remote sensor, a radiation reference optical remote sensor, real-time processing and mission planning equipment, etc. The multispectral wide-swath optical remote sensor is mounted on satellite A, the real-time processing and mission planning equipment is mounted on satellite A, and the infrared radiation reference optical remote sensor is mounted on satellite B. Satellite A and satellite B operate on the same orbital plane, with satellite A's orbital phase leading satellite B by a fixed value. Step 4: The satellite A real-time processing and mission planning equipment calculates the visible time window of the above calibration area by the satellite B radiation reference optical remote sensor, and uses it as the planned time node. Step 5: If the radiation reference optical remote sensor of satellite B is visible to the above calibration area, the real-time processing and mission planning equipment of satellite A generates mission guidance and sends it to satellite B through the inter-satellite link. Step 6: After receiving the mission guidance information, the radiation reference optical remote sensor on satellite B will point the observation field of view to the above-mentioned calibration area at the planned time node, and after completing the imaging, it will send the observation data to satellite A through the inter-satellite link; Step 7: The satellite A real-time processing and mission planning equipment calculates the calibration coefficients based on the observation data of the above calibration area using the satellite A multispectral wide-swath optical remote sensor and the satellite B radiation reference optical remote sensor, and performs radiation calibration on the satellite A multispectral wide-swath optical remote sensor. If the satellite A multispectral wide-swath optical remote sensor observes a deep, cold, and uniform cloud layer, this cloud layer can be used as a calibration area, and steps four through seven can be executed.

[0029] Furthermore, in step one, the ground calibration area is a uniformly radiated site, and the ground-based equipment is used to transmit the data to satellite A for real-time processing and mission planning.

[0030] Furthermore, in step three, the radiation references of satellite A and satellite B are transferred. A standard calibration source is configured on the radiation reference optical remote sensor of satellite B, and the calibration coefficients can be transferred to the multispectral wide-swath optical remote sensor of satellite A by observing the same calibration area.

[0031] Furthermore, the planned time node in step six is ​​preferably the overpass time of satellite B over the target, which is obtained by the real-time processing and mission planning equipment of satellite A based on the orbital parameters of satellite B.

[0032] Furthermore, the calibration coefficients in step seven are preferably calculated through steps such as inter-channel position matching, calculation of simulated apparent radiance based on atmospheric transport model, calculation of spectral matching factor, and fitting of calibration equation.

[0033] The following description, in conjunction with the accompanying drawings, further illustrates this embodiment, which implements the autonomous radiation reference transfer method for satellite optical remote sensor formations.

[0034] like Figure 2As shown, assume that satellites A and B are in formation and orbit in the same plane at an altitude of 500 km. Satellite A carries a multi-band wide-swath optical remote sensor, observing the visible, short-wave, mid-wave, and infrared spectrums, primarily for Earth surveys and cloud detection. Simultaneously, satellite A is equipped with real-time processing and mission planning equipment for autonomously planning ground calibration area observation missions, autonomously observing the ground calibration area according to planned timelines, and generating guidance information to coordinate with satellite B to complete ground calibration area observations. Satellite A can also autonomously discover areas suitable for radiation benchmark transfer, such as deep convective clouds. Satellite B carries a radiation benchmark optical remote sensor, observing the short-wave to long-wave spectrum, and can serve as a high-precision radiation measurement satellite. By observing the same calibration area as satellite A, it transfers a high-precision space radiation measurement benchmark to satellite A's multi-band wide-swath optical remote sensor.

[0035] First, ground-based calibration areas that meet the requirements are identified, such as Qinghai Lake, snow-capped mountains, and grasslands. The geographic information of these calibration areas is then uploaded to the satellite A real-time processing and mission planning equipment. Based on the geographic information of the calibration areas and the satellite orbit information, the satellite A real-time processing and mission planning equipment continuously plans the time window for each orbit of the satellite A multi-spectral wide-swath optical remote sensor to observe the calibration areas. Simultaneously, it processes the observation data from the satellite A multi-spectral wide-swath optical remote sensor in real time, acquiring the positioning information and cloud detection results of the observation data.

[0036] When the time window for reaching the calibration area arrives, the real-time processing and mission planning equipment of Satellite A analyzes whether the observation data contains the geographical location of the calibration area on the ground. If it does, and there is no cloud cover over the calibration area, then the calibration area can be used by Satellite B to transfer the radiation reference to Satellite A. The observation data of the above calibration area is put into memory and recorded as observation data 1. Based on the orbit and calibration area geographic information of Satellite B, the real-time processing and mission planning equipment of Satellite A accurately calculates the time window and field-of-view pointing angle for the radiation reference optical remote sensor of Satellite B to observe the aforementioned calibration area, and generates mission guidance information. The mission guidance information is sent from Satellite A to Satellite B through the inter-satellite link. After receiving the mission guidance information, the radiation reference optical remote sensor of Satellite B points its field of view to the aforementioned calibration area according to the planned time node. After completing the observation, the observation data of the aforementioned calibration area (denoted as observation data 2) is sent back to Satellite A through the inter-satellite link.

[0037] After receiving observation data 2, the satellite A real-time processing and mission planning equipment retrieves observation data 1 from memory, performs inter-channel position registration between observation data 1 and observation data 2, calculates the simulated apparent radiance and spectral matching factor based on the atmospheric transmission model, obtains the calibration equation and calibration coefficients using a fitting method, completes the radiometric correction of the satellite A multi-band wide-swath optical remote sensor, and realizes the transfer of the satellite B radiometric reference to satellite A.

[0038] In addition, when the satellite A multispectral wide-swath optical remote sensor observes a deep, cold, and uniform cloud layer, this cloud layer can be used as a calibration area. The above steps can be used to achieve on-orbit autonomous search of the calibration area and transfer of the radiation reference.

[0039] This invention relates to the field of on-orbit radiometric calibration, and in particular to an autonomous radiometric reference transfer method for satellite optical remote sensor formations. It provides an on-orbit autonomous radiometric calibration method for satellite formations; it can autonomously discover calibration areas suitable for radiometric reference transfer in orbit, breaking the limitation of the limited number of ground calibration fields, and autonomously complete collaborative observation and radiometric reference transfer among multiple satellites.

[0040] Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention. Unless otherwise specified, the embodiments and features described in this application can be arbitrarily combined with each other.

Claims

1. A method for autonomous radiometric reference transfer in a satellite optical remote sensor formation, characterized in that, Satellite A's multi-band wide-swath optical remote sensor observes the Earth, identifies cloud-free calibration fields or uniform regions suitable for reference transfer, generates mission guidance information, and transmits it to Satellite B via an inter-satellite link. Satellite B's radiation reference optical remote sensor points its observation field of view to the designated area based on the mission guidance information and sends the observation data back to Satellite A via the inter-satellite link. After radiation reference transfer calculations, calibration parameters are obtained, and radiometric correction is performed on Satellite A's multi-band wide-swath optical remote sensor, completing the radiation reference transfer.

2. The autonomous radiometric reference transfer method for satellite optical remote sensor formations according to claim 1, characterized in that, include: Step 1: Satellite A plans the time window for calibration of the radiation reference transfer area; Step 2: Satellite A's multispectral wide-swath optical remote sensor performs Earth observation imaging, real-time positioning, and cloud detection; Step 3: During the time window, when the observation image of the satellite A multispectral wide-swath optical remote sensor covers the calibration area and there are no clouds, the ground is used as the calibration area; If the satellite A multispectral wide-swath optical remote sensor observes a deep, cold, and uniform cloud layer, that cloud layer will be used as the calibration area. Step 4: Satellite A calculates the visible time window of the calibration area for the radiation reference optical remote sensor of Satellite B, and uses it as the planned time node; Step 5: If the calibration area is visible to the radiation reference optical remote sensor of satellite B, then satellite A generates mission guidance in real time and sends it to satellite B via inter-satellite link; Step 6: After receiving the mission guidance information, the radiation reference optical remote sensor on satellite B will point the observation field of view to the calibration area at the planned time node, and after completing the imaging, it will send the observation data to satellite A through the inter-satellite link; Step 7: The satellite A real-time processing and mission planning equipment calculates the calibration coefficients based on the observation data of the calibration area using the satellite A multispectral wide-swath optical remote sensor and the satellite B radiation reference optical remote sensor, and performs radiation calibration on the satellite A multispectral wide-swath optical remote sensor.

3. The autonomous radiometric reference transfer method for satellite optical remote sensor formations according to claim 2, characterized in that, In step one, the ground calibration area is a uniformly radiated site, and the ground-based equipment is used to transmit the data to satellite A for real-time processing and mission planning.

4. The autonomous radiometric reference transfer method for satellite optical remote sensor formations according to claim 2, characterized in that, The standard calibration source is configured on the radiation reference optical remote sensor of satellite B. The calibration coefficients are transferred to the multispectral wide-swath optical remote sensor of satellite A by observing the same calibration area from both satellite A and satellite B.

5. The autonomous radiometric reference transfer method for satellite optical remote sensor formations according to claim 1, characterized in that, Satellite A and Satellite B operate on the same orbital plane, with Satellite A having a fixed orbital phase that is ahead of Satellite B.

6. The autonomous radiometric reference transfer method for satellite optical remote sensor formations according to claim 2, characterized in that, The planned time node is the time when satellite B passes over the target, which is obtained by the real-time processing and mission planning equipment of satellite A based on the orbital parameters of satellite B.

7. The autonomous radiometric reference transfer method for satellite optical remote sensor formations according to claim 2, characterized in that, The calibration coefficients are obtained through a series of steps, including inter-channel position matching, calculation of simulated apparent radiance based on an atmospheric transport model, calculation of spectral matching factors, and fitting of calibration equations.

8. A satellite system, characterized in that, Including Satellite A and Satellite B; Satellite A is equipped with real-time processing and mission planning equipment, which is used for autonomous planning of ground calibration area observation missions, autonomous observation of ground calibration areas according to planned time nodes, and generation of guidance information to coordinate with Satellite B to complete ground calibration area observations. Satellite B transmits the space radiation measurement benchmark to the multispectral wide-swath optical remote sensor of Satellite A by viewing the same calibration area as Satellite A.

9. The satellite system according to claim 8, characterized in that, The satellite formation autonomously searches for calibration areas in orbit.

10. The satellite system according to claim 9, characterized in that, When the satellite A multispectral wide-swath optical remote sensor observes a deep, cold, and uniform cloud layer, that cloud layer is used as the calibration area.

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